The present invention relates to a novel type of prostaglandin E and ulcer preventive agents containing the same.
Prostaglandin is a generic term for various prostanoic acids and is classified into various groups, such as E, F, A, B, C, D, and H, according to the manner in which keto and/or hydroxyl groups are introduced in five-membered ring portions. Prostaglandins will stimulate the uterine muscle and, in addition, they have various physiological and pharmacological actions, such as vasodilation, inhibition of platelet aggregation, and inflammatory action.
Prostaglandin E (hereinafter referred to as PGE), as a substance with a five-membered ring structure, has a group represented by: ##STR1## Broadly, there are known two types of PGE, namely, PGE.sub.1 in which the carbon--carbon bond at the 5- and 6-positions (C.sub.5 -C.sub.6 bond) is a single bond: ##STR2## and PGE.sub.2 in which the C.sub.5 -C.sub.6 bond is a double bond: ##STR3## PGE.sub.2, for example, is known as having antiulcer activity on one hand, but on the other hand it has such actions as uterine contraction, intestine contraction, and vasodilation; further it is recognized as having side effects, such as severe alvine flux. Therefore, it is unsuitable or impossible to use PGE.sub.2 as antiulcers.
Whilst, it has been recognized that in human or animal metabolites there are present free substances similar to prostaglandin E in which C.sub.13 -C.sub.14 bond is saturated and in which the carbon at the 15-position forms a carbonyl group. These substances, or species of 13,14-dihydro-15-keto prostaglandin E are: ##STR4## These corresponds to PGE.sub.1, PGE.sub.2, and 6-keto PGE.sub.1 respectively, and they are known as substances which are naturally metabolically produced in vivo through enzymic metabolic reaction. These species of 13,14-dihydro-15-keto PGE have been reported as physiologically and pharmacologically inactive metabolic products which exhibit little of the various physiological activities of PGE (Acta Physiologica Scandinavica, Vol 66, p. 509.about., 1966), and has been regarded as such. Therefore, little has been expected of the pharmacological effect of these metabolic products and compounds similar to them.